From 60bb6c2322fd14a90b0dab500d0ab468b4a3fd4a Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Thu, 4 Jun 2026 22:25:59 +0100
Subject: [PATCH] Add support for TypeForm in incremental mode

---
 mypy/types.py                         |  3 ++-
 test-data/unit/check-incremental.test | 23 +++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/mypy/types.py b/mypy/types.py
index 6e934f64315c0..da420d1c012d2 100644
--- a/mypy/types.py
+++ b/mypy/types.py
@@ -3688,11 +3688,12 @@ def deserialize(cls, data: JsonDict) -> Type:
     def write(self, data: WriteBuffer) -> None:
         write_tag(data, TYPE_TYPE)
         self.item.write(data)
+        write_bool(data, self.is_type_form)
         write_tag(data, END_TAG)
 
     @classmethod
     def read(cls, data: ReadBuffer) -> Type:
-        ret = TypeType.make_normalized(read_type(data))
+        ret = TypeType.make_normalized(read_type(data), is_type_form=read_bool(data))
         assert read_tag(data) == END_TAG
         return ret
 
diff --git a/test-data/unit/check-incremental.test b/test-data/unit/check-incremental.test
index 22f0c805799bb..9647393cdac66 100644
--- a/test-data/unit/check-incremental.test
+++ b/test-data/unit/check-incremental.test
@@ -8116,3 +8116,26 @@ tmp/m.py:5: note: Revealed type is "builtins.str"
 tmp/m.py:4: note: Revealed type is "def () -> builtins.int"
 tmp/m.py:5: error: Incompatible types in assignment (expression has type "type[A]", variable has type "int")
 tmp/m.py:6: note: Revealed type is "builtins.str"
+
+[case testTypeFormWorksInIncrementalMode]
+import b
+[file a.py]
+from typing import TypeVar
+from typing_extensions import TypeForm
+
+T = TypeVar("T")
+def test(arg: TypeForm[T]) -> T: ...
+
+[file b.py]
+from a import test
+test("int")
+
+[file b.py.2]
+from a import test
+reveal_type(test("int"))
+
+[builtins fixtures/primitives.pyi]
+[typing fixtures/typing-full.pyi]
+[out]
+[out2]
+tmp/b.py:2: note: Revealed type is "builtins.int"